After making Raymond Chandler his sleuth (the implausible A Paramount Kill), Larsen now sets Dorothy L. Sayers, Agatha Christie, and their fellow members of the 1930's Detection Club (E.C. Bentley, A.A. Milne) to discover who killed the gentleman in Dorothy's parlor. Dorothy says she doesn't know him, but her bluster is soon seen through by the gratingly timorous Agatha, who discovers: that Dorothy's husband, the alcoholic Mac, was the intended victim; that two members of his WW I regiment have also died under suspicious circumstances; and that each had received a white feather in the mail--the ancient military symbol for cowardice. Forming an edgy partnership, the two mystery grande dames plot, interrogate, connive, and confront Mac's old war chums and their families, while trying to sidestep an abrasive young American writer who's demanding an interview--or does she have a secret agenda? A mildly effective period piece, with some interesting oddments--a cold potato as gun-silencer, for instance--and diverting clues, but mostly forced and dry.